JP2000334468A - Method for reducing and adjusting ozone concentration - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the concentration of dissolved ozone in ozone-containing water without requiring maintenance by bringing the ozone-containing water into contact with glass. SOLUTION: Ultrapure water is sent from an ultrapure water tank 1 to an ejector 3 and a gaseous ozone-oxygen mixture generated in an ozonizer 4 is blown into the ejector 3. A vapor-liquid mixed state is formed and the ozone is dissolved to produce ozone-containing water. This ozone-containing water is transported to a flow pipe 5 in the vapor-liquid mixed state, passed through a crushed glass packed column 7 attached to the pipe 5 and brought into contact with the glass. The type of the glass used here is not particularly limited but borosilicate glass is perferable. The shape of the glass is not particularly limited and plate glass, glass tubes or glass beads may be used. Since the self-decomposition of the dissolved ozone in the ozone-containing water is promoted by contact with the glass, the concentration of the dissolved ozone is reduced without requiring maintenance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for reducing and adjusting an ozone concentration. More specifically, the present invention relates to a method for reducing the concentration of dissolved ozone, which can reduce the concentration of dissolved ozone without the need for maintenance in the treatment of wastewater containing ozone, and a wet cleaning process for electronic materials and the like. And an ozone concentration adjusting method capable of easily supplying ozone-containing water having a desired dissolved ozone concentration to a use point.

[0002]

2. Description of the Related Art Removal of fine particles, organic substances, metals, and the like from the surface of electronic materials such as silicon substrates for semiconductors, glass substrates for liquid crystals, and quartz substrates for photomasks is necessary to ensure product quality and yield. Very important. For this purpose, wet cleaning is performed at a high temperature using a concentrated chemical based on hydrogen peroxide, which is a so-called RCA cleaning method, and a mixed solution of ammonia and hydrogen peroxide (APM) or hydrochloric acid and hydrogen peroxide is used. Mixed solution (HPM)
And so on. The use of these cleaning methods reduces the cost of chemical solutions, the cost of ultrapure water for rinsing, the cost of waste liquid treatment, and the cost of air conditioning that exhausts chemical vapors and creates clean air. In recent years, in order to reduce the burden on the environment such as mass disposal of drugs and emission of exhaust gas, the wet cleaning process has been reviewed in recent years. The present inventors have previously developed gas-dissolved cleaning water for cleaning electronic materials in which ozone is dissolved in pure water. Washing water in which ozone is dissolved in pure water exhibits extremely high oxidizing power, while the dissolved ozone concentration is as low as several mg / liter.
It is used in a process of removing contamination by impurities such as organic substances and metals attached to the surface of an electronic material, and in a process of uniformly oxidizing the surface of a silicon substrate to form a chemical oxide film layer. The cleaning water obtained by dissolving ozone in pure water has the advantage that the surface of the object to be cleaned is kept clean because there is no persistence, and high-purity water is re-used by the decomposition or removal of ozone, and can be reused. However, in the washing water in which ozone is dissolved, the dissolved ozone is self-decomposed with time to become oxygen, and thus it is not easy to maintain and manage the ozone concentration. On the other hand, the present inventors have found that the ozone-containing gas and pure water are supplied while being mixed in the water supply pipe, whereby the decrease in the dissolved ozone concentration is suppressed, and the ozone concentration is substantially constant. A system for supplying ozone-containing water was developed. That is, a mixed gas of ozone and oxygen is produced by an ozone generator, and is fed into pure water in an ozone dissolving apparatus. The mixed gas of ozone and oxygen is mixed with pure water to form a gas-liquid mixed state, the ozone is dissolved to generate ozone-containing water, and further flows through the water flow pipe in the gas-liquid mixed state. Ozone dissolved in water changes to oxygen over time due to self-decomposition, but the decrease in dissolved ozone due to self-decomposition is compensated by the ozone in the gas phase being dissolved in water. The concentration can be kept almost constant. But,
Also in this system, the ozone concentration may decrease when the branch pipe that leads the ozone-containing water to the use point passes through a complicated pipe path. Further, ozone-containing water having a different ozone concentration may be required depending on the use point. Japanese Patent Application Laid-Open No. 10-57907 discloses a method of stably supplying ozone water having a constant concentration by setting the supply amount of ozone water obtained by the ozone water production means higher than the maximum discharge amount of ozone water. There has been proposed a method of controlling the amount of ozone water in an ozone water tank so that the amount of ozone water is always within a certain range. However, in such a method, control is complicated and large-scale equipment is required. Ozone-containing water used in the electronics industry such as semiconductors and liquid crystals is required to have a very high purity for impurities other than ozone. In addition, ozone-containing water is widely used for washing and disinfection in fields such as the pharmaceutical industry and the food industry, but at present there is almost no method for adjusting the dissolved ozone concentration while maintaining high purity. There is a need for a method for adjusting the ozone concentration that can easily obtain ozone-containing water having a desired concentration. On the other hand, ozone remains in the ozone-containing water used at the point of use, and similarly to ozone-containing water not used at the point of use, the ozone decomposition treatment can be performed using activated carbon, an ultraviolet irradiation device, a catalyst, or the like. Is being done. However, ultraviolet irradiation requires high equipment costs and processing costs, and the activated carbon and the catalyst deteriorate.

[0003]

SUMMARY OF THE INVENTION The present invention relates to a method for reducing the concentration of dissolved ozone without the need for maintenance in the treatment of wastewater containing ozone, and a method for reducing the concentration of ozone, electronic materials, and the like. It is an object of the present invention to provide an ozone concentration adjusting method capable of easily supplying ozone-containing water having a desired dissolved ozone concentration to a point of use in the wet cleaning step.

[0004]

The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, by bringing ozone-containing water into contact with glass, self-decomposition of dissolved ozone is promoted. It has been found that the ozone concentration is reduced, and that by selecting the contact conditions between the ozone-containing water and the glass, it becomes possible to control the amount of ozone decomposed to obtain the desired concentration of ozone-containing water. Based on the above, the present invention has been completed. That is, the present invention
(1) a method for reducing the ozone concentration of ozone-containing water, which comprises bringing the ozone-containing water into contact with glass; and
(2) An object of the present invention is to provide a method for adjusting the ozone concentration of ozone-containing water, wherein the ozone-containing water is brought into contact with glass to obtain a desired concentration of ozone-containing water. Further, as a preferred embodiment of the present invention, (3) the ozone concentration according to item (1), wherein the ozone-containing water is brought into contact with the glass by making a part of the liquid contact material of the ozone-containing water passage into glass. (4) The method for reducing the ozone concentration according to (1), wherein the ozone-containing water is brought into contact with the glass by installing a container filled with crushed glass in the flow path of the ozone-containing water, (5) The method for adjusting the ozone concentration according to (2), wherein the ozone-containing water is brought into contact with the glass by making a part of the liquid contact material of the water passage of the ozone-containing water into glass, and (6). The method for adjusting the ozone concentration according to item (2), wherein the ozone-containing water is brought into contact with the glass by installing a container filled with the crushed glass in the flow path of the ozone-containing water, may be mentioned.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The method for reducing ozone concentration according to the present invention comprises bringing ozone-containing water into contact with glass, and the method for adjusting ozone concentration according to the present invention comprises bringing ozone-containing water into contact with glass to obtain a desired concentration. Ozone-containing water. By contacting the ozone-containing water with the glass, the self-decomposition of dissolved ozone in the ozone-containing water is promoted.By contacting the ozone-containing wastewater with the glass, the concentration of the dissolved ozone can be reduced without requiring maintenance. Can be reduced. In addition, in a washing step of an electronic material or the like, ozone-containing water in which ozone is dissolved at or above a desired concentration at a point of use can be produced and brought into contact with glass in the vicinity of the point of use to reduce the amount of dissolved ozone to a desired concentration. There is no particular limitation on the type of glass used in the method of the present invention, for example, soda lime glass, potassium lime glass, borosilicate glass, lead glass,
Aluminosilicate glass, borate glass, phosphate glass, aluminate glass, titanate glass, fluoride glass, chalcogen glass, and the like can be given. Among them, borosilicate glass excellent in chemical durability against water and acid can be preferably used. The shape of the glass used in the method of the present invention is not particularly limited, and examples thereof include plate glass, glass tubes, glass beads, and glass fibers. In the method of the present invention, there is no particular limitation on the method of bringing ozone-containing water into contact with glass. Alternatively, the ozone-containing water can be brought into contact with the glass by installing a container filled with crushed glass in the flow path of the ozone-containing water. Among these, the crushed glass that crushed the glass to about several mm square,
Since it is easy to handle and has a large surface area, it can be suitably used.

According to the method for adjusting ozone concentration of the present invention,
In an ozone dissolving device, excess ozone is dissolved in pure water, and before being used at the point of use, the ozone-containing water is brought into contact with glass to promote self-decomposition of ozone,
The concentration of ozone-containing water can be easily adjusted. Further, the concentration of dissolved ozone in the ozone-containing wastewater can be easily reduced by the same means. That is, in the contact between the ozone-containing water and the glass, the concentration of the ozone-containing water can be easily and accurately adjusted by selecting the surface area of the glass to be contacted, the contact time, and the like. The amount of ozone decomposed can be increased by means such as increasing the amount of glass that is brought into contact with the ozone-containing water, reducing the particle size of the crushed glass, or reducing the water flow rate. In carrying out the method of the present invention, using crushed glass to be used, the relationship between the glass filling amount and the amount of ozone decomposition, the relationship between the glass particle size and the amount of ozone decomposition, the relationship between the water flow rate and the amount of ozone decomposition, etc. Is experimentally obtained in advance, and a desired ozone concentration can be obtained by controlling an arbitrary factor in accordance with the amount of ozone to be reduced. In addition, since the amount of ozone decomposition is also affected by the ozone concentration of the ozone-containing water, it is preferable to change the ozone concentration of the ozone-containing water and conduct an experiment when grasping the relationship between the contact conditions with glass and the amount of ozone decomposition. . According to the method of the present invention, in a supply system of ozone-containing water in an electronic material factory or the like, a container filled with crushed glass or the like is provided between an ozone-containing water production device and a point of use of ozone-containing water, thereby achieving high efficiency. The dissolved ozone concentration of the ozone-containing water having a low concentration can be reduced, and the ozone-containing water having a desired concentration can be easily obtained. During the contact with the glass, the ozone-containing water must not be contaminated, so that the piping through which the ozone-containing water flows has very little elution of foreign substances and does not react with strong oxidizing ozone.
It is preferable to use a tube made of a fluororesin or the like.
Similarly, the container filled with the crushed glass is also preferably a member having high ozone resistance. The container itself for filling the crushed glass may be made of glass.

In the method of the present invention, the mechanism by which the ozone-containing water is brought into contact with the glass to promote the self-decomposition of ozone is not clear, but it is presumed that a trace amount of metal mixed in the glass acts. Is done. However, the metal is hardly eluted from the glass and is below the detection limit even when analyzed.Therefore, even if the ozone-containing water that has been brought into contact with the glass is used for cleaning electronic materials and the like, the metal becomes a contamination source. There is no danger. FIG. 1 is a process flow chart of an embodiment of the method of the present invention. Ultrapure water is sent from the ultrapure water tank 1 to the ejector 3 by the pump 2, and at the same time, a mixed gas of ozone and oxygen generated by the ozone generator 4 is blown into the ejector, and the gas is mixed into the water pipe 5 in a gas-liquid mixed state. Sent. A crushed glass packed column 7 is provided near the use point 6 in the water passage pipe. Sampling points 8 and 9 provided before and after the crushed glass packed column
In, the conditions are set such that a desired concentration of ozone-containing water is obtained at the point of use by sampling the ozone-containing water and measuring the respective dissolved ozone concentrations. When the ozone concentration reduction method of the present invention is carried out in a drain line of ozone-containing water used at a point of use or unused ozone-containing water, unlike a conventional method using activated carbon, ultraviolet irradiation, a catalyst, and the like, As a completely maintenance-free ozonolysis method, the concentration of dissolved ozone can be reduced. When the method for adjusting ozone concentration of the present invention is performed to obtain ozone-containing water at a desired concentration, unlike conventional methods of decomposing ozone by contacting with activated carbon or a catalyst, glass deteriorates like activated carbon or a catalyst. In addition, there is no possibility that foreign matter is eluted and the quality of the ozone-containing water is lowered.

[0008]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the present invention. Example 1 The ozone concentration of ozone-containing water was adjusted using the apparatus shown in FIG. Ultrapure water is sent from the ultrapure water tank 1 to the ejector 3 by the pump 2 at a flow rate of 16 l / min.
At the same time, a mixed gas of ozone and oxygen generated by the silent discharge type ozone generator 4 was blown into the ejector and sent to the water pipe 5 in a gas-liquid mixed state. In the water flow pipe, a crushed glass packed column 7 is provided near the use point 6, and the
It is filled with 500 g of 1.2 mm thick glass [Corning Co., Pyrex 7740] crushed into 5 mm square.
At sampling points 8 and 9 before and after the crushed glass packed column, ozone-containing water
Each time, sampling was performed, and the dissolved ozone concentration of each sample was measured. The dissolved ozone concentration of the ozone-containing water before passing through the crushed glass column was 25 to 26 mg / l, and the dissolved ozone concentration after passing through the crushed glass column was 14 to 15 mg / l. Example 2 The same operation as in Example 1 was repeated except that the supply amount of the mixed gas of ozone and oxygen was reduced. The dissolved ozone concentration of ozone-containing water before passing through a crushed glass packed column is 15 to 17 mg
/ Liter, and the dissolved ozone concentration of the ozone-containing water after passing through the crushed glass packed column was 8 to 9 mg / liter. Example 3 The same operation as in Example 1 was repeated, except that the supply amount of the mixed gas of ozone and oxygen was further reduced. The dissolved ozone concentration of the ozone-containing water before passing through the crushed glass packed column is 10 ~
The dissolved ozone concentration after passing through the column packed with crushed glass was 6 to 7 mg / liter. Example 4 Assuming the treatment of ozone-containing wastewater, the filling amount of crushed glass in the apparatus shown in FIG. 1 was increased, and the dissolved ozone concentration of the supplied ozone-containing water was reduced. The same operation as in Example 1 was repeated, except that the amount of glass to be filled in the crushed glass packed column was 600 g and the supply amount of the mixed gas of ozone and oxygen was reduced. The dissolved ozone concentration of the ozone-containing water before passing through the crushed glass packed column is 5 to 7 mg / liter,
The dissolved ozone concentration of the ozone-containing water after passing through the crushed glass column was 3 to 4 mg / liter. Example 5 The same operation as in Example 4 was repeated, except that the supply amount of the mixed gas of ozone and oxygen was further reduced. The dissolved ozone concentration of ozone-containing water before passing through a crushed glass packed column is 2-3
mg / l, and the dissolved ozone concentration of the ozone-containing water after passing through the crushed glass packed column was 1-2 mg / l. Example 6 Except that the filling amount of crushed glass was increased to 1,000 g,
The same operation as in Example 5 was repeated. The dissolved ozone concentration of ozone-containing water before passing through a column packed with crushed glass is 2-3 mg /
Liter, and the dissolved ozone concentration of the ozone-containing water after passing through the column packed with crushed glass was 0.3 to 0.4 mg / liter. Table 1 shows the results of Examples 1 to 6.

[0009]

[Table 1]

As can be seen from Table 1, by passing ozone-containing water having a high dissolved ozone concentration through a column filled with crushed glass and contacting it with the glass, the dissolved ozone concentration is reduced and the ozone-containing water is reduced five times. Since the dispersion of the measured value of the dissolved ozone concentration is about 1 mg / liter, it is understood that the dissolved ozone concentration of the ozone-containing water can be accurately controlled by the method of the present invention. Further, from the results of Examples 4 to 6 in which ozone-containing water having a low dissolved ozone concentration was passed, the method of the present invention
It is also effective for the treatment of ozone-containing wastewater. Comparing Example 5 and Example 6, the amount of dissolved ozone in the treated water can be effectively increased by increasing the amount of crushed glass filled in the column. You can see that.

[0011]

According to the method of the present invention, high-concentration ozone-containing water can be produced, dissolved ozone can be decomposed by a very simple treatment, and the concentration of ozone-containing water can be adjusted accurately and stably to a desired concentration. it can. Also, in the treatment of ozone-containing waste water, the concentration of dissolved ozone can be reduced by using a maintenance-free device.

[Brief description of the drawings]

FIG. 1 is a process flow chart of an embodiment of the method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ultrapure water tank 2 Pump 3 Ejector 4 Ozone generator 5 Water supply piping 6 Use point 7 Crushed glass packed column 8 Sampling point 9 Sampling point

Claims (2)

[Claims] 1. A method for reducing the ozone concentration of ozone-containing water, comprising bringing the ozone-containing water into contact with glass. 2. A method for adjusting the ozone concentration of ozone-containing water, wherein the ozone-containing water is brought into contact with glass to obtain a desired concentration of ozone-containing water.